We shall continue our studies on silicate transport in diatoms and mitochondria. We shall attempt to characterize and define the mechanism of silicate accumulation, i.e., whether this process is (1) energy dependent, (2) in response to delta pH across the mitochondrial inner membrane, or (3) in exchange with accumulated mitochondria anions. BIBLIOGRAPHIC REFERENCES: C.W. Mehard and B.E. Volcani. Silicon-containing granules of rat liver, kidney and spleen mitochondria. Electron probe X-ray microanalysis. Cell Tiss. Res. 174: 315-327 (1976). C.W. Mehard and B.E. Volcani. Silicon in rat liver organelles: electron probe microanalysis. Cell Tiss. Res. 166: 255-263 (1976).